Water heater having a waterway changeover control apparatus and method for operating the same

ABSTRACT

A water heating system and method of operating the same. The system includes a first water heater having a first heating source of a first type. The system further includes a second water heater having a second heating source of a second type. A valve having a first interface that is connected to the cold water source, a second interface that is connected to a first cold water inlet of the first water heater, a third interface that is connected to a second hot water outlet of the second water heater, and a fourth interface connected to the hot water outlet of the first water heater. A motor positions the changeover valve to one of at least three positions. A control circuit includes a temperature sensor near the first hot water outlet of the first water heater, and a controller coupled to the first temperature sensor and the motor.

BACKGROUND

The invention relates to a water heater having a waterway changeovercontrol apparatus and its related control method.

Storage electric water heaters, gas water heaters, and solar waterheaters are example water heaters with their own advantagesrespectively. Among them, the electric water heater, installed in thewall cabinet or balcony, includes features of long service life, energyefficiency, safety, and environmental protection. However, it needspreheating prior to use and its continuous water supply typically cannotexceed its volume (i.e., the water temperature will drop after largeamounts of water is used). The instaneous gas water heater can supplyhot water while the gas is burning, so that there is no limit on the hotwater supply quantity. But due to the drainage of cold water in the pipeafter startup, one needs to wait to use, and if one switches off the hotwater during use, then the water temperature may be a little bit highafter restart. The solar water heater can heat up the water by the sun,which is energy-saving, environmentally beneficial, and economic.However, the solar water heater has shortcomings such as complicatedinstallation, inconvenient maintenance, long cold water pipe, andpossible failure in cloudy or rainy days or in winter.

Although there are technical plans to join the electric water heater andthe gas or solar water heater, two water heaters need switchingindependently, which is not only inconvenient, but also fail to make thebest use of both water heaters. The patent of China No. 200520004940.4,has introduced an electric water heater that can be used jointly withsolar energy. The solar water heater is connected to the electric waterheater by a signal line. Below the electric water heater, there is apipe to connect it to a mixing valve, and then valves to connect theelectric water heater and the solar water heater. This connection methodis not only complicated, but makes many changes to the original pipes ofthe user and has poor applicability.

SUMMARY

In one embodiment, the invention presents a waterway changeover controlapparatus for a water heater, so that two types of water heaters, forexample the electric water heater and the gas or solar water heater, canhave a basis to work together. This allows the resultant water heater toadopt the advantages and avoid shortcomings of both water heaters, aswell as to give full play to their advantages.

In a more specific embodiment of the invention, the waterway changeovercontrol apparatus includes a changeover valve that is under the controlof a control circuit. The changeover valve has a first interface toconnect the cold water source, a second interface to connect the coldwater inlet of the first water heater, a third interface to connect thehot water outlet of the second water heater, and a fourth interface toconnect the hot water outlet of the first water heater, as well as atleast three switching positions. When the changeover valve is in thefirst position, only the first interface is interconnected to the secondinterface. When the changeover valve is in the second position, only thesecond interface is interconnected to the third interface. When thechangeover valve is in the third position, only the third interface isinterconnected to the fourth interface. The control circuit can includean MCU and a first temperature sensor at the hot water outlet of thefirst water heater. The outlet terminal of the first temperature sensoris connected to a corresponding signal input terminal of the MCU, andthe output terminal of the MCU to the control terminal of the changeovervalve.

A more specific construction of the water heater can be the changeovervalve having a fourth position, and when it is in the fourth position,the third interface is interconnected to the second and fourthinterfaces at the same time.

The control circuit of the waterway changeover control apparatus can beinstalled on the changeover valve or in the water heater, or installedalone. The connections at the input and output terminals of the MCUinclude a wired connection and a wireless communication connectionthrough a wireless transceiver.

With the help of this invention, two types of water heaters can beconveniently combined together, and by means of control circuit, theautomatic switching necessary between two water heaters can be realized.

For example, when an electric water heater is combined with a gas waterheater, if the water temperature in the electric water heater is higher,the changeover valve is located in the first position, the cold watersource is connected to the water storage tank of the electric waterheater, and the electric water heater works alone. When the heatingcapacity of the electric water heater is insufficient and fails toensure hot water supply, the changeover valve is switched to the secondposition. The hot water outlet of the gas water heater is connected tothe water storage tank of the electric water heater, so that the coldwater in the outlet pipe of the gas water heater flows to the waterstorage tank of the electric water heater, and then, the changeovervalve is switched to the third position. When the changeover valve isswitched to the third position, the hot water outlet of the gas waterheater is connected to the hot water outlet of the electric waterheater, so that the gas water heater will supply hot water alone to keepcontinuous hot water supply.

For another example, when an electric water heater is combined with asolar water heater, the hot water in the solar water heater will be usedat first due to the environmental protection and the energy savingcharacteristics of the solar water heater. At the time, the changeovervalve is in the second position, the cold water in the solar waterheater is drained into the electric water heater when there is hot waterin the electric water heater, and then, the changeover valve is switchedto the third position and the solar water heater supplies hot wateralone.

If the changeover valve is in the fourth position, the hot water outletof the gas or solar water heater is connected to both the hot wateroutlet and water storage tank of the electric water heater. In this way,two water heaters will supply hot water together.

As a result, some embodiments of the invention can not only make theelectric water heater or gas water heater to supply hot water alone, butalso can realize: 1) a series connection between two water heaters—whenthe heating capacity of the electric water heater is insufficient, thegas or solar water heater can compensate; 2) a parallel connectionbetween two water heaters—when the hot water supply of the electricwater heater is insufficient, the gas or solar water heater can supplyhot water. When the changeover valve is in the second position, theoutlet of the gas or solar water heater is connected to the waterstorage tank of the electric water heater, so that the retained coldwater in the outlet pipe can be drained into the water storage tank ofthe electric water heater. Then, the changeover valve is switched to thethird position, and the gas or solar water heater supplies hot wateralone. At the time, due to the retained cold water draining into thewater storage tank of the electric water heater, the problem of coldwater drainage of a gas or solar water heater prior to use can besolved, thereby avoiding waste of water.

One examplary procedure of switching control by the control circuit inthe waterway changeover control module for the water heater is asfollows:

Step 1: With the changeover valve in its first position, confirm if thewater temperature rise (monitored by a first temperature sensor) at theoutlet of the first water heater is higher than a preset value. Thisdetermines if the user started to use water. If yes, then go to Step 2,otherwise, keep monitoring.

Step 2: Confirm if the water temperature reaches the peak value based onthe preset conditions. If yes, then go to Step 3, otherwise, keepmonitoring.

Step 3: Confirm if the water temperature drop after reaching the peakvalue exceeds the allowed threshold value. If yes, then go to Step 4,otherwise, keep monitoring.

Step 4: Switch the changeover valve to its second position and hold itthere for a certain time, in order to drain the retained cold water fromthe pipe into the water storage tank of the first water heater.

Step 5: Switch the changeover valve to the third position, so that onlythe second water heater supplies water.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structure diagram of Example I of the invention.

FIG. 2 is a schematic diagram of Example I.

FIGS. 3 (A), (B), (C) and (D) is a schematic diagram for the first,second, third, and fourth positions, respectively, of the changeovervalve in Example I.

FIG. 4 is a control circuit diagram of Example I.

FIG. 5 is a control process block diagram of Example I.

FIG. 6 is a control process block diagram of Example II of theinvention.

FIG. 7 is a structure diagram of Example III of the invention.

FIG. 8 is a schematic diagram of Example III.

FIG. 9 is a control process block diagram of Example III.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

Example I

The waterway changeover control apparatus for a water heater 100 (mayalso be referred to herein as a water heating system 100) is shown inFIGS. 1 and 2. The water heater 100 includes the changeover valve C thatis under the control of a control circuit. Reference A is a storageelectric water heater, as the first water heater, and reference B is agas water heater (such as an instantaneous gas water heater), as thesecond water heater. The valve C, shown in FIG. 3, has four interfaceswith an approximately ninety degree interval between each other. Thefirst interface 1 is connected to the cold water source, the secondinterface 2 is connected to the cold water inlet of the electric waterheater A, the third interface 3 is connected to the hot water outlet ofthe gas water heater B, and the fourth interface 4 is connected to thehot water outlet of the electric water heater A. In addition, the valveC has three main switching positions. When the valve C is in the firstposition, as shown in FIG. 3 (A), only the first and second interfacesare interconnected; i.e. the cold water source is connected to the waterstorage tank of the electric water heater A, at the time, the cold watercan be filled into the water storage tank. When the valve C is in thesecond position as shown in FIG. 3 (B), only the second and thirdinterfaces are interconnected; i.e. the hot water outlet of the gaswater heater B is connected to the water storage tank of the electricwater heater A, at the time, the retained cold water in the pipe can bedrained into the water storage tank. When the valve C is in the thirdposition as shown in FIG. 3 (C), only the third and fourth interfacesare interconnected; i.e. the hot water outlet of the gas water heater Bis connected to the hot water outlet of the electric water heater A, atthe time, the gas water heater B supplies hot water. The valve C has thefourth switching position as shown in FIG. 3 (D), where the thirdinterface 3 is connected to both second interface 2 and fourth interface4, at the time, the hot water outlet of the gas water heater B isconnected to both hot water outlet and water storage tank of theelectric water heater A.

The control circuit, referring to FIG. 4, includes an MCU and the firsttemperature sensor S1 near the hot water outlet of the electric waterheater A. The output terminal of the first temperature sensor isconnected to the corresponding signal inlet terminal AD1 of MCU (e.g.,Renesas Electronics America, model no. R5F212K4), and the outputterminal of MCU to the valve motor M—the controlled terminal of thevalve C through driver IC IC2003 (e.g., Texas Instrument Model No.ULN2003).

After the waterway changeover control apparatus for water heating system100 in this example starts up, it allows selecting the electric mode orgas mode. If the intelligent mode is selected, the switching controlprocedures of the control circuit are shown as FIG. 5.

Step 1: At first, with the valve C in its first position, confirm if thewater temperature rise RT (monitored by the first temperature sensor)near the outlet of the first water heater A is higher than a set value(e.g., three degrees Celsius), to determine if the user starts to usewater. If yes, then go to Step 2, otherwise, keep monitoring.

Step 2: Confirm if RT reaches the peak value based on the presetconditions that the water temperature stops rise for more than a timeperiod (e.g., 1 minute); if yes, then go to Step 3, otherwise, keepmonitoring.

Step 3: Confirm if the water temperature RT after reaching the peakvalue has dropped below a threshold value (e.g., 45 degrees Celsius). Ifyes, then go to Step 4, otherwise, keep monitoring.

Step 4: The motor M starts and switches the valve C to its secondposition and keep it there for a time period (e.g., three minutes), inorder to drain the retained cold water from the pipe into the waterstorage tank of the electric water heater A.

Step 5: The motor M starts and switches the valve C to its thirdposition, so that only gas water heater B supplies water, thus tocontinuously supply hot water. It has been found that example I has atleast one or more of the following improvements when compared with theprior water heating systems:

1. When the water supply in the electric water heater A is insufficient,it can switch to the gas water heater B automatically, and the switchingprocess is stable and reliable.

2. The cold water period problem is solved well, because the retainedcold water in the pipe of the gas water heater B is drained into thewater storage tank of the electric water heater A, instead of supplyingto the user directly. When the water from the gas water heater Bsupplies directly to the user in Step 4 and 5, the cold water has beenalready drained completely into the water storage tank of the electricwater heater A, so that there is only hot water at the water outlet.

3. The changeover operation can make the best use of the electric andgas water heaters A and B, to give full play to their advantages. Innormal conditions, the water volume in the electric water heater A isenough for the user to use. However, for winter season or many users,the system can identify automatically if the water volume is sufficientor not, and when insufficient, the system can start up the gas waterheater B automatically. The startup and changeover processes are stable,without the problem of a cold water period nor the problem of hot andthen cold water supply. If the user would like to use the gas waterheater B and meanwhile avoid the problem of the cold water period, theuser can start when the water is heated to a set point (e.g., 45 degreesCelsius) by the electric water heater A in the fast mode, so that thewaiting time is very short.

4. The retained cold water of the gas water heater B may be draineddirectly or stored in another container by the user in general, whilethis example can save water and provide convenience to the user.

5. When the water supply is switched from the electric water heater A tothe gas water heater B, the water temperature of the gas water heater Bcan be sensed intelligently. If the temperature is too high, it willforce the water temperature to make a gradual change, to remind theuser.

6. Each time after a bath of the user, for example, the water heatingsystem can reset automatically, without any influence to the next use.

Example II

This example is similar to Example I in the basic structure. Onedifference is, besides the first temperature sensor S1 installed nearthe hot water outlet of the electric water heater A for measuringRT_(electric), there is the second temperature sensor installed near theoutlet of the gas water heater B for measuring RT_(gas).

The control process is shown in FIG. 6. After startup, the MCU startsthe rotation of the motor M for valve C at first, to prevent it fromadhesion, and then, confirm if the intelligent mode that combines theelectric and gas water heaters A and B is selected. If yes, then thewaterway changeover control apparatus for water heating system 100 willbe controlled as follows:

Step 1: With the valve C in its first position, confirm if the watertemperature RT_(electric) (measured by the first temperature sensor)rises continuously by a preset value (e.g., three degrees Celsius), todetermine if the user starts to use water.

Step 2: Confirm if RT_(electric) reaches the peak value based on thepreset conditions that the water temperature stops rise for more than 1min. If yes, then go to Step 3, otherwise, keep monitoring.

Step 3: Confirm if the water temperature RT_(electric) after reachingthe peak value has dropped below a threshold value (e.g., 45 degreesCelsius). If yes, then go to Step 4, otherwise, keep monitoring.

Step 4: The motor M switches the valve C to its second position and thecontroller confirms if the water temperature RT_(gas) measured by thesecond temperature sensor S2 is higher than RT_(electric) measured bythe first temperature sensor. If no, then keep monitoring. If yes, thenturn the valve C to its third position by a preset angle (e.g., thirtydegrees) and after the preset time interval (e.g., ten seconds), measurethe temperature rise of RT_(gas), to avoid the water temperature frombeing too high.

Step 5: Confirm if the RT_(gas) rise exceeds the allowed threshold value(e.g., four degrees Celsius) within the preset time interval. If yes,then the motor M switches the valve C to its third position after thepreset time (e.g., one minute). Otherwise, it will put the valve C toits third position directly. Finally, only gas water heater B supplieswater; i.e. to continuously supply hot water. In this way, anyoverheating of the water due to fast temperature rise can be avoided.

In the above-mentioned process, the valve C has the fourth position,where the third interface is connected to both the second and fourthinterfaces. The hot water outlet of the gas water heater B is connectedto both the hot water outlet and water storage tank of the electricwater heater A, so that the gas and electric water heaters A and B willwork together to provide sufficient hot water. If the operation isstopped or the combination is canceled according to detection, the clearoperation is carried out to reset the valve C.

Example III

The waterway changeover control apparatus for water heating system 100of this example is shown in FIGS. 7 and 8. One difference with ExampleIII is that the second water heater is a solar water heater D. Theconnections of the valve C can refer to Example I. Refer to FIG. 4 forcontrol circuit. The first temperature sensor S1 and the second one S2are installed near the hot water outlet of the electric and solar waterheaters A and D, respectively.

After startup, when the energy efficiency mode is selected, theswitching control procedures of the control circuit are shown in FIG. 9,as follows:

Step 1: With the valve C in its second position, confirm if the watertemperature rise T_(outlet) (monitored by the first temperature sensor)of the first water heater A is higher than a preset value (e.g., threedegrees Celsius), to determine if the user starts to use water. If yes,then go to Step 2, otherwise, keep monitoring.

Step 2: Confirm if the water temperature T_(outlet) (measured by thefirst temperature sensor) of the electric water heater A is higher thanthe a preset value (e.g., 45 degrees Celsius). If no, then the motor Mstarts and switches the valve C to its third position and makes thesolar water heater D supply hot water. If yes, then go to Step 3.

Step 3: The motor M starts and switches the valve C to its secondposition, which drains the retained cold water from the outlet pipe ofthe solar water heater D into the water storage tank of the electricwater heater A. The step confirms if the cold water is drained outcompletely based on the preset conditions. In one example, theconditions are: the temperature T in the outlet pipe of the solar waterheater D rises up continuously (e.g., by three degrees Celsius) andkeeps at the temperature for more than a time period (e.g., one minute),or drains the water continuously for more than a time period (e.g., oneperiod). If no, then keep monitoring. If yes, then go to Step 4.

Step 4: Confirm if the water temperature T_(solar) (measured by thesecond temperature sensor) of the solar water heater D is lower than apreset value (e.g., 45 degrees Celsius). If no, then the motor M startsand switches the valve C to its third position and makes the solar waterheater D supply hot water until the water temperature drops lower than apreset threshold (forty degrees Celsius). At this time, switch the valveC to its first position and have the electric water heater A supply hotwater. If yes, then go to Step 5.

Step 5: The motor M starts and switches the valve C to its fourthposition, so that the solar water heater D and electric water heater Asupply water jointly.

After this, the water temperature T_(outlet) is monitored to confirm ifit is within a range (e.g., 43-47 degrees Celsius). If no, then make thesystem 100 the requirement by further regulation.

Therefore, the hot water in the solar water heater D will be used to thegreatest extent by the user while the hot water of the electric waterheater A is only supplied as compensation, thereby saving energy.

Besides the above-mentioned examples, the invention has other applicablemethods. For example, a temperature sensor can be installed at the waterstorage tank and the water outlet of the electric water heater A as wellas the water outlet of the gas water heater B respectively. Their outputterminals are connected to the corresponding signal input terminals ofthe control circuit (including the MCU). The sensors outputT_(tank)−temperature of the probe on the top of the water storage tank,T_(water)−outlet water temperature of the electric water heater A, andT_(gas)−outlet water temperature of the gas water heater B. Therefore, amore precise control can be realized. Any technical proposal resultingfrom equivalent replacement or equivalent transformation falls into theprotective range of this invention.

Thus, the invention provides, among other things, a new and useful waterheater having a water changeover control apparatus and method foroperating the same. Various features and advantages of the invention areset forth in the following claims.

1. A water heating system comprising: a first water heater having afirst heating source of a first type, a first cold water inlet, and afirst hot water outlet; a second water heater having a second heatingsource of a second type, a second cold water inlet connected to a coldwater source, and a second hot water outlet; a valve having a firstinterface connected to the cold water source, a second interfaceconnected to the first cold water inlet of the first water heater, athird interface connected to the second hot water outlet of the secondwater heater, a fourth interface connected to the hot water outlet ofthe first water heater, a motor positioning the changeover valve to oneof at least three positions including a first position defined by thefirst interface being interconnected to the second interface, a secondposition defined by the second interface being interconnected to thethird interface, and a third position defined by the third interfacebeing interconnected to the fourth interface a control circuit includinga temperature sensor near the first hot water outlet of the first waterheater, a controller coupled to the first temperature sensor and themotor and configured to control the motor based on a sensed temperatureby the temperature sensor.
 2. The water heating system of claim 1,wherein the motor further positions the changeover valve to a fourthposition defined by the third interface being interconnected to thesecond and fourth interfaces concurrently.
 3. The water heating systemof claim 1, wherein the second type is different from the first type. 4.The water heating system of claim 1, wherein the first heating source ofthe first type includes an electric heating source and the secondheating source of the second type includes a gas heating source, and thefirst water heater is a storage water heater and the second water heateris an instantaneous water heater.
 5. The water heating system of claim1, wherein the first heating source of the first type includes anelectric heating source and the second heating source of the second typeincludes a solar heating source.
 6. The water heating system of claim 5,wherein the control circuit further includes a second temperature sensornear the second hot water outlet of the second water heater, and thecontroller is further configured to control the motor based on a secondsensed temperature by the second temperature sensor.
 7. The waterheating system of claim 1, wherein the control circuit further includesa second temperature sensor near the second hot water outlet of thesecond water heater, and the controller is further configured to controlthe motor based on a second sensed temperature by the second temperaturesensor.
 8. The water heating system of claim 1, wherein the first waterheater includes a storage tank, the control circuit further includes asecond temperature sensor near the second hot water outlet of the secondwater heater and a third temperature sensor near the storage tank, andthe controller is further configured to control the motor based on asecond sensed temperature by the second temperature sensor and a thirdsensed temperature by the third temperature sensor.
 9. A method ofcontrolling the water heater of claim 1, the method comprising:controlling the motor to position the valve in the first position;monitoring the sensed temperature for a temperature value; monitoringthe sensed temperature for a temperature variation; determining if thetemperature variation is greater than a first set value; determining ifthe sensed temperature traverses the temperature value; controlling themotor to move the valve from the first position to the second positionafter the temperature variation is greater than the first set value andthe sensed temperature traverses the temperature value; maintaining themotor at the second position for a time period; and controlling themotor, after the time period, to position the valve in the thirdposition.
 10. A method of controlling the water heater of claim 7, themethod comprising: controlling the motor to position the valve in thefirst position; monitoring the sensed temperature for a firsttemperature value; monitoring the sensed temperature for a temperaturevariation; determining if the temperature variation traverses a firstset value; determining if the sensed temperature traverses the firsttemperature value; controlling the motor to position the valve in thesecond position after the temperature variation traverses the first setvalue and the sensed temperature traverses the first temperature value;monitoring the second sensed temperature for a second temperature value;determining if the second sensed temperature is greater than the firstsensed temperature; and controlling the motor to move the valve from thesecond position toward the third position after determining the secondsensed temperature is greater than the first sensed temperature.
 11. Themethod of claim 10, further comprising: monitoring the second sensedtemperature for a second temperature variation; determining if thesecond temperature variation traverses a second set value within a timeinterval; and controlling the motor to move the valve to the thirdposition after the time interval when determining the second temperaturevariation traverses the second set value within the time interval. 12.The method of claim 11, further comprising: controlling the motor tomove the valve to the third position when determining the secondtemperature variation does not traverse the second set value within thetime interval.
 13. A method of controlling the water heater of claim 6,the method further comprising: controlling the motor to position thevalve in the first position; monitoring the sensed temperature for afirst temperature value; monitoring the sensed temperature for atemperature variation; determining if the temperature variation isgreater than a first set value; determining if the sensed temperaturetraverses the first temperature value; controlling the motor to positionthe valve from the first position to the second position after thetemperature variation is greater than a first set value and the sensedtemperature traverses the first temperature value; monitoring the secondsensed temperature for a second temperature value, determining if thesecond sensed temperature is greater than the first sensed temperature;and controlling the motor to move the valve from the second positiontoward the third position after determining the second sensedtemperature is greater than the first sensed temperature.
 14. The methodof claim 13, further comprising: monitoring the second sensedtemperature for a second temperature variation; determining if thesecond temperature variation traverses a second set value within a timeinterval; and controlling the motor to move the valve to the thirdposition after the time interval when determining the second temperaturevariation traverses the second set value within the time interval. 15.The method of claim 14, further comprising: controlling the motor tomove the valve to the third position when determining the secondtemperature variation does not traverse the second set value within thetime interval.